1. Field of the Invention
This invention relates to a process of and an apparatus for recovering energy or power from top gas exhausted from a blast furnace, and more particularly to an improvement in a process of and an apparatus for recovering energy or power from said top gas exhausted from a blast furnace while a dry moving bed type dust collector is used for final dust removal from said exhaust gas.
2. Description of the Prior Art
In compliance with the current uplift of consensus for saving energy, there have been proposed and used various types of apparatus and processes which are intended for recovering energy or power from the top gas exhausted from blast furnaces through driving a gas turbine by the energy possessed by the top gas.
Usually, the top gas exhausted from blast furnace contains a large amount of dust, and it is necessary to remove this dust from the gas before the gas is fed to the gas turbine. FIG. 1 shows a typical conventional system for removing the dust from the top gas. This system has a dust catcher 2 adapted to catch and remove relatively coarse dust particles suspended in the top gas exhausted from a blast furnace 1. The gas is then delivered to a venturi scrubber (wet type dust collector) 3 and supplied to a top pressure recovery turbine 4 to drive the latter. The gas exhausted from the turbine 4 then passes through a wet type electric precipitator 5 for precipitation of dust and finally forwarded to a gas holder 6.
In this conventional system, however, the temperature of the gas entering the top pressure recovery turbine is inconveniently decreased to 40.degree. C. or so, because of the use of the wet type dust collector (venturi scrubber). Also, the pressure drop across the wet type dust collector is as large as 2000 to 2500 mmAq. As a result, the efficiency of recovery of pressure is rendered impractically low. At the same time, the low gas temperature permits the use of only the centrifugal type turbine which has only a small efficiency. In addition, the life of the turbine blades is shortened due to a large concentration of dust which is as large as 20 mg/Nm.sup.3. Further, the use of wet type dust collector inevitably necessitates the use of equipments for water disposal and drying of dusts, resulting in a considerably raised cost of installation and running cost of the system.